One doesn’t get a second chance to make a first impression. Grammatical errors can leave a poor impression and make one appear unprofessional. I wasn’t taught about when and how to use apostrophes during my schooling and I have reason to suspect that I’m not alone. An article by Nick Daws  in Writers’ Monthly in May 1994 taught me when and how to use apostrophes and this is summarised below.
Apostrophes are always required in:
Contractions (can’t, shouldn’t)
Expressions showing possession or association (David’s football, the girl’s book)
Apostrophes are needed even if the noun is inanimate or abstract (the table’s legs, 20 years’ service).
Not required in:
Plurals (tables, books, people).
Nick Dawes stated “Even professional writers are confused at times by where they should place the possessive apostrophe…”
“Its” is the possessive form of “it”
“It’s” means “it is” or “it has.”
The University of Bristol agree that “it’s” and “its” cause all sorts of problems and it takes just 2 minutes it takes to learn the difference between them. On their website  they give the following examples:
“It’s been a long time since we spoke,” he whispered (it has).
“Come on,” he shouted, “it’s a lovely day!” (it is).
“There is no way it’s going to be ready on time” (it is).
“It’s been ready for weeks!” (it has).
“Its,” without an apostrophe, is a possessive form, where an apostrophe is usually required. It is similar to words like his and hers, neither of which needs an apostrophe.
The building was missing its doors and windows.
The tree had lost all of its leaves.
Has your chewing gum lost its flavour?
Madrid is famous for its art galleries.
To figure out which is correct for your sentence, just swap in “it is” and then “it has.” If the sentence makes sense with either of those substitutions, use it’s. If the resulting sentence doesn’t make sense, use its.